1. Field of the Invention
The present invention relates to apparatus for preventing the formation and dripping of condensate which accumulates on the inlet pipes of liquid heaters such as water heaters.
2. Description of the Prior Art
Heaters of various types have long been used for heating cold water or other liquids which circulate through a conduit system within the heating unit. One of the best known of such heaters is the household water heater of the type which has a generally cylindrical heater jacket enclosing a burner element, for burning a gaseous fuel, and a heating coil which forms part of the conduit system through which the liquid to be heated circulates. The heating coil is usually a helical conduit and is located generally above the burner element such that the heat produced by the burner is adequately transferred to the coil and thus to the water circulating within it. A flue or stack is provided in the top of heater jacket for venting the fumes resulting from the combustion of the gas in the burner element.
The cold water to be heated enters the water heater through a portion of the circulating conduit which is referred to as the inlet pipe. The inlet pipe generally enters the bottom portion of the heater jacket and extends upwardly through the water heater interior where it is joined to the heating coil. The inlet pipe is usually positioned adjacent to the burner and is exposed to the heat coming from the burner. Because the water which is circulated through the water heater is at its coldest temperature at the inlet pipe, there is a relatively large temperature gradient between the water entering the heater through the inlet pipe and the heated air surrounding the inlet pipe adjacent the heater burner. As the circulating water is carried up and through the heating coil, the temperature gradient between the liquid and the surrounding air within the heater is reduced because of the rapid rate at which the water is heated.
The relatively cold temperature of the water as it enters the heater through the inlet pipe and the generally high temperature of the heated air surrounding the inlet pipe causes the exterior surface of the inlet pipe to be at a temperature which is usually below the dew point of the air within the heater. As a result, air-borne liquid contained within the heater jacket condenses out of the air in the form of condensate accumulating on the inlet pipe. Such condensation is generally limited to the inlet pipe where the temperature differential between the water within the pipe and the heated air surrounding the inlet pipe is the greatest. Other portions of the circulatory conduit are not generally affected by condensate because they are usually positioned above the burner element and the strong draft of hot air from the burner tends to vaporize or carry away any condensate which might tend to accumulate on that portion of the circulating conduit.
The presence of condensate on the inlet pipe of a water heater causes problems in several regards. When such condensate drips off of the inlet pipe and onto the area surrounding the water heater, it can accumulate in large quantities over an extended period of time and cause an unsightly condition and possibly damage the surface on which it accumulates. In addition, if there is a significant amount of unburned gaseous fuel emitted from the burner element in the heater, this fuel also condenses on the inlet pipe. Such accumulations of fuel may prove hazardous under certain operating conditions wherein they may ignite.
One of the most serious problems which results from the condensation of airborne liquid on the inlet pipe of a water heater is the corrosion and eventual destruction of the inlet pipe or portions of the water heater upon which the condensation accumulates. Because the inlet pipe and water heater are typically constructed of metal, the continual presence of water or other liquids can cause the oxidation of metal, such as the rusting of steel. In addition to oxidation of metals which can result from the presence of water, other forms of chemical corrosion are encountered when the fuel burned in the water heater produces sulfur dioxide. As is well known, sulfur dioxide usually combines with water to produce sulfurous acid which can be very damaging to various metals. This aggravates and compounds the corrosion problem presented by the mere presence of water. Obviously, the corroding effect of water and sulfurous acid may cause the weakening or total destruction of the inlet pipe or water heater. This would result in replacement or repair of the heater, the inlet pipe or other portions of the circulatory conduit.
Various attempts have been made in the past to reduce this problem of condensation on the inlet pipe of this type of water heater. Generally, these attempts have been directed primarily at the reenforcement of the inlet pipe and the surrounding area. The purpose of such reenforcing is to provide a thicker wall for the conduit where the condensation most frequently accumulates and to thus increase the life of the pipe portions which would normally be corroded away by the presence of condensate. It has also been common in the past to provide drip pans and the like in the base of the heater to accumulate the condensate which runs off of the intake pipe. While such drip pans prevent the condensate from dripping out of the water heater and onto the surrounding area, they do not reduce the presence of the potentially corrosive condensate on the inlet pipe.